Recently it was discovered that van der Waals-bonded magnetic materials retain long range magnetic ordering down to a single layer, opening many avenues in fundamental physics and potential applications of these fascinating materials. One such material is FePS3, a large spin (S=2) Mott insulator where the Fe atoms form a honeycomb lattice. In the bulk, FePS3 has been shown to be a quasi-two-dimensional-Ising antiferromagnet, with additional features in the Raman spectra emerging below the Neel temperature of approximately 120 K. Using magneto-Raman spectroscopy as an optical probe of magnetic structure, we show that one of these Raman-active modes in the magnetically ordered state is actually a magnon with a frequency of of approximately 3.7 THz (122 cm-1). Contrary to previous work, which interpreted this feature as a phonon, our Raman data shows the expected frequency shifting and splitting of the magnon as a function of temperature and magnetic field, respectively, where we determine the g-factor to be approximately 2. In addition, the symmetry behavior of the magnon is studied by polarization-dependent Raman spectroscopy and explained using the magnetic point group of FePS3.
@article{arxiv.1908.00608,
title = {Quasi-Two-Dimensional Magnon Identification in Antiferromagnetic FePS3 via Magneto-Raman Spectroscopy},
author = {Amber McCreary and Jeffrey R. Simpson and Thuc T. Mai and Robert D. McMichael and Jason E. Douglas and Nicholas Butch and Cindi Dennis and Rolando Valdes Aguilar and Angela R. Hight Walker},
journal= {arXiv preprint arXiv:1908.00608},
year = {2020}
}